<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>flex</title>
    <style>
        .box {
            width: 400px;
            height: 400px;
            border: 1px solid red;
            display: flex;
            flex-wrap: wrap;
        }

        .box div {
            width: 0;
            height: 100px;            
        }
        .one{
            order: 2;
            background-color: aliceblue;
            flex: 1;
        }
        .two{
            order: 1;
            background-color: aquamarine;
            flex: 2;
        }
        .three{
            order: 3;
            background-color: aqua;
            flex: 1;
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="one">one</div>
        <div class="two">two</div>
        <div class="three">three</div>
        
    </div>
</body>

</html>